Data services of the GSM (Global System for Mobile communications) have launched a new era of mobile communications. The early analog cellular modems had become unattractive to the market, as they were slow and unreliable. Now the market for data is moving onwards (more bursty) and upwards (more traffic), and the standardization institutes are working towards higher data rates but more significantly also towards packet data services. This will certainly broaden the appeal to end-users because data is routed more efficiently through the network and hence at lower costs, and also access times are reduced.
The general trend is for data applications to generate increasingly bursty data streams; this results in inefficient use of circuit switched connections. Moreover, fixed networks have seen an enormous growth in data traffic, not at least because of the rise of Internet access demand, such that it is to be supposed that mobile networks will spread as technology and customer expectations move on. The current GSM switch network is based on narrow band ISDN (Integrated Services Digital Network) circuits, so that the reason for rate limitations moves from the access network to the core network.
The new GPRS (General Packet Radio Services) network will offer operators the ability to charge by the packet, and support data transfer across a high-speed network at up to eight times slot radio interface capacity. GPRS introduces two new nodes into the GSM network, a SGSN (Serving GPRS Support Node) and a GGSN (Gateway GPRS Support Node). The SGSN keeps track of the location of the mobile terminal within its service area and sends and receives packets to/from the mobile terminal, passing them on or receiving them from the GGSN. The GGSN then converts the GSM packets into other packet protocols (e.g. IP or X.25) and sends them out into other networks.
UMTS will deliver advanced information directly to people and provide them with access to new and innovative services. It will offer mobile personalized communications to the mass market regardless of location, network or terminal used. In the basic network architecture according to 3GPP Release '99, as defined in the 3GPP technical specification TS 23 060 (Version 3.6.0, 2001-01), two or more CN (core network) domains can be connected to one RNC (radio network controller) or a similar unit, e.g. RNAS (Radio access network Access Server), in the radio access network. Moreover, a UE (user equipment) or a mobile terminal or MS (mobile station) have an independent relation to the two (or more) CN domains, i.e. separate MM (mobility management) connections, such that the two (or more) CNs are “uncoordinated”.
In the two CNs, switching control is performed by circuit switched (CS) MSCs (Mobile Switching Centers) and packet switched (PS) 3G SGSNs, respectively, which have no interactions with each other. Both of them have a functionality of their own. When an MS has no CS services in use, the MSC sees its MM state “MM idle”. When the MS has no PS services in use, or it has PDP (packet data protocol) contexts, but it has not shown any activity for a long time, it is in a PMM (packet mobility management) state “PMM idle” from the 3G SGSN's point of view. When the MS has an ongoing PS or CS connection, it has established an RRC (Radio Resource Control) connection towards the RNC. This means that the MS performs either handovers, cell updates or URA (UMTS Registration Area) up-dates, depending of the channels it uses and the level of activity it has shown lately. From the CNs' point of view, the MS is in the MM state “MM-connected” (via MSC) or in the PMM state “PMM-connected” (via 3G SGSN). The RNC includes both CRNC-C (Controlling RNC C-plane) and SRNC-C (Serving RNC C-plane) functionalities in the same physical entity. The CN sees RNCs mapped to LAs (location areas) in the MSC or to RAs (routing areas) in the 3G SGSN.
The MS may have only a PS connection in use. Thus, it is PMM-connected in the 3G SGSN and RRC-connected in the RNC, but the MSC sees the MS in state “MM-idle”. If an incoming call arrives at the MSC, the MSC sends a paging message to all RNCs, which serve the LA the MS, has registered to. If there are several RNCs serving the same LA, paging is sent to the RNC(s) where (an) RRC connection(s) exist(s), but also to RNC(s), which do not know the MS. Thus, unnecessary extra pagings are performed.
Furthermore, the MS may have an NRT PDP (Non-Real Time Packet Data Protocol) context in use, the RAB (Radio Access Bearer) of which has been released due to low level of activity. After that, the MS establishes a CS call and enters to the MM state “RRC-connected”. During the call, the 3G SGSN may receive data packets related to the NRT PDP context. The 3G SGSN then assumes that the MS is in the PMM state “PMM-idle” and sends a paging request to all RNCs, which are mapped to serve the corresponding RA. However, in one of the paged RNCs, the MS's RRC connection already exists, while all other RNCs perform unnecessary extra pagings.
Thus, signalling load on radio interface paging channels is significantly increased due to pagings from “unnecessary” cells.